Cured latex article and method of making same

ABSTRACT

A method for making rubber latex articles such as surgeon&#39;&#39;s gloves which are hyperallergenic and which permit improved epidermal perception through the article. The method comprises curing the inside and outside surfaces of a coagulated latex film by contacting the surfaces with sulfur monochloride until the film is cured sufficiently so the film will recover its original shape when the film is stretched and released.

United States Patent Inventor Appl. No.

Filed Patented Assignee Los Angeles, Calif.

Continuation-impart of application Ser. No. 720,853, Apr. 12, 1968, nowabandoned.

CURED LATEX ARTICLE AND METHOD OF S H as surgeon's gloves which arehyperallergenic and which permit improved epidermal perception throughthe article. The U.S. Cl 264/306, method comprises curing the inside andoutside surfaces of a 2/ 168,264/307 coagulated latex film by contactingthe surfaces with sulfur Int.Ci B29h 3/04 monochloride until the film iscured sufficiently so the film Field of Search 264/307, will recover itsoriginal shape when the film is stretched and 306; 2/168 released.

0/! FORM /4' ['fllGl/Al/V 7' 0/ f0? nv Auaanun'x (WM/MM; ,va z'z/anrmrsPrimary Examiner-Robert F. White Assistant Examiner-J. R. HallAttorneys- Leigh B. Taylor, Paul R. Wylie and Harold R.

Beck

ABSTRACT: A method for making rubber latex articles such Emit HIV/SHIPf7! CURED LATEX ARTICLE AND METHOD OF MAKING SAME This is acontinuation-in-part of copending application Ser. No. 720,853filed Apr.12, 1968 now abandoned.

This invention relates generally to a method for making a rubber latexarticle. The invention is more specifically directed to the manufactureof a novel rubber latex surgeon glove using the inventive method.

A glove for covering the hand of a surgeon is necessary to preventinfection of the patient. One the better gloves made in the prior artwas manufactured by dissolving milled rubber in a petroleum distillatesolvent. A hand-shaped form was then dipped into the rubber solution.The solvent was then permitted to evaporate leaving a thin deposit ofrubber on the hand-shaped form. It was then necessary to again dip theform into the rubber solution and to again permit the solvent toevaporate so that more rubber would be deposited on the form. It wasfrequently necessary to dip the hand-shaped form and permit the solventto evaporate as many as seven or more times until a sufficient rubberdeposit was made on the form. The process of forming the glove was timeconsuming, required a petroleum solvent and required initial milling ofthe rubber which adversely effected the strength of the rubber article.The rubber article was then cured which was frequently accomplished byexposing the article to sulfur monochloride.

The method of curing rubber articles with sulfur monochloride originatedbecause it was difficult in the prior art to incorporate curing agentsdirectly into the rubber. The sulfur monochloride curing process washowever considered unsatisfactory in that it was difficult to controlthe vapor concentration and therefore difficult to control the amount ofcuring of the article. When the rubber solution method of manufacturingrubber articles appeared, the sulfur chloride curing process wasgenerally continued; however, the process began to be replaced byincorporating curing agents directly into the rubber solution.

A further advance, in the manufacture of articles made from thin filmsof rubber, was made when rubber latex replaced the use of rubbersolutions. Articles of rubber film were easily made using latex systemsbecause it was necessary to dip the form only once into the latex toobtain the necessary quantity of rubber on the form. No explosivesolvents were used and water was used as the carrier for the colloidalrubber in the latex system. No mastication or milling of the rubber wasnecessary when the latex system was used, therefore, the rubber articlehad greater strength. It was easier to mix curing agents directly intothe latex system and in addition less time was needed to manufacture thearticle. The manufacture of the latex article was also substantiallyless expensive.

Since vulcanizing and curing agents could be easily incorporated intothe latex system the sulfur chloride method of curing rubber wascompletely avoided when latex was used. Because of the above advantages,articles made from latex film replaced substantially all of thefilm-type articles formed from rubber solution. For example, surgeonsgloves which were formerly formed from rubber solution have been almostcompletely replaced with latex surgeon's gloves.

Notwithstanding the low cost of manufacturing the later glove, manysurgeons prefer the much more expensive glove formed from rubbersolution. The surgeons who continue to use the glove formed from rubbersolution, which is known in the trade as the brown milled" glove, claimthat they are better able to feel through the glove and that the glovedoes not cause an allergenic reaction. It is known that the hands ofsome surgeons become sensitive when they use the latex-type glove. Inaddition, latex-type gloves frequently have a somewhat undesirablesurface tackiness.

Accordingly, it is an object of this invention to provide an articlesuch as a surgeon's glove which is hyperallergenic and which permitsimproved epidermal perception.

It is a further object of this invention to provide a latex film articlewhich is substantially free from surface tack.

Another object of this invention is to provide an inventive method formanufacturing a novel surgeon's glove which has the advantages of boththe latex and brown milled" type surgeon's gloves.

The invention contemplates a method of making a rubber latex article bythe steps of contacting a form for the article with a rubber latex fluidthus forming a film of latex rubber which may be natural rubber latex,on the form, removing water from the film and then curing the film bycontacting both surfaces of the film with sulfur monochloride underconditions which will cause vulcanization. Of particular importance isthe fact that the rubber latex fluid from which the initial film isformed does not contain the usual compounding curing agents.

The invention also contemplates a novel natural rubber latex surgeon'sglove that has advantageous properties imparted thereto by the foregoingmethod of manufacture.

It also may be desirable to leach the film after the initialfilm-forming step to remove water soluble impurities therefrom.

The article formed in accordance with the above process will behyperallergenic and will permit improved epidermal perception.Satisfactory control of curing can be obtained by contacting the formedfilm with an external vulcanizing agent. Since there are no internalvulcanizing agents which can be activated inadvertently by exposure tohigher temperatures, the cure of the natural rubber latex articlesformed according to this invention can be controlled by the length oftime the article is in contact with the external vulcanizing atmosphere.vulcanization can be stopped almost immediately upon removing thenatural rubber latex article from the vulcanizing atmosphere, whether itbe a vapor contact or dipping in a sulfur monochloride containingsolution.

FIG. 1 is a view of a natural rubber latex film as deposited on ahand-shaped form in the initial dipping operation;

FIG. 2 illustrates a finished surgeon's glove made according to theinvention and shown in a cufied position; and

FIG. 3 is a flow diagram illustrating the various steps of a preferredmethod for making surgeons gloves according to the invention.

Referring now to the drawing, a surgeon's glove is formed according tothe inventive method by first dipping a form 10 which is shaped as ahand in a suitable coagulant for natural rubber latex. A solution ofcalcium nitrate is preferred as a coagulant. However, other coagulantsthat are well known in the art can be used, including other polyvalentmetal salts. The form coated with the coagulant is then dipped into anatural rubber latex fluid. The latex fluid can contain constituentswhich are commonly compounded with rubber including pigments,reinforcing agents and the like. However, it has been discovered inaccordance with this invention that it is the compounded curing agentswhich seem to cause the allergenic reactions. In the case of surgeonsgloves, it is preferred to have only a suitable antioxidant present inan amount sufficient to inhibit autocatalytic oxidation. Suchantioxidant will be typically a secondary aromatic amine such asphenol-bnapthyl amine. Inasmuch as the gloves fabricated according tothe inventive method do not require a compounded curing or vulcanizingagent, the natural rubber latex fluid will be free of vulcanizingconstituents which are the ingredients believed to be responsible forallergenic reactions.

After removal from the dipping operation, form 10 will have a relativelythin layer of uncured natural latex rubber formed as a film ll thereon.The dipping time is controlled so that a single clip will deposit a filmthat will form a cured glove having a preferred thickness of from about0.004 to about 0.012 inches. The film, while still on the form, isleached to remove water soluble impurities therefrom. The leachingoperation can be accomplished by either water spray or immersion inwater. The film is then air-dried to remove the water so that a reactionwill not occur between water and the sulfur monochloride which comes incontact with the glove during the curing step.

In the first curing step, the glove on the form is placed in a curingoven at an elevated temperature sufficient to heat the forms and glovesto that temperature. Sulfur monochloride is then introduced into theoven. The sulfur monochloride vaporizes at the elevated temperatureproducing a vulcanizing atmosphere around the glove. The gloves are keptin the vulcanizing atmosphere until they are sufficiently cured topermit the gloves to be removed from the form. The gloves are thenrotated in an atmosphere of sulfur monochloride until an optimum cure isreached. When the gloves are properly cured they will not crack whenstretched (which would indicate overcuring) and the gloves will offerresistance to stretching and demonstrate complete recovery whenstretched and released (the absence of which would indicateundercuring). The oven is then exhausted and fresh air is introduced tostop the curing cycle.

Variations in the curing temperature and exposure time combination canbe used. Once the cure time for any combination of sulfur monochlorideconcentration and temperatures which will result in an adequately curedglove in an oven is determined, the glove can be controllably curedsimply by controlling the time that the glove remains in the vulcanizingatmosphere.

An article such as a glove manufactured in accordance with the abovemethod will not cause skin sensitivity, that is, the article ishyperallergenic. The article will permit better epidermal perceptionthrough the film than was possible through a prior art latex glovehaving a comparable thickness. The method of manufacture has most of theadvantages of the latex system. Only one dip into the latex isnecessary, no solvent is necessary and there is no reduction of strengthdue to milling or mastication. A rubber latex surgeon's glovemanufactured by the novel process herein disclosed has the advantages ofthe brown milled and prior art latex gloves.

While not wishing to be bound by any particular theory, it is believedthat the improved epidermal perception in the latex article is due to asurface cure which hardens the surfaces but leaves an uncured orslightly cured area between the surfaces. It is believed that thehyperallergenic character is caused by the absence of curing orvolcanizing agents which were present in the prior art latex film.

The following specific example illustrates the invention and showsspecific conditions which can be used within the scope thereof to form asurgeons glove.

SPECIFIC EXAMPLE A number of surgeons gloves are prepared by dippinghand-shaped forms in a natural rubber latex mixture containing onlylatex and phenol-b-napthyl amine.

The forms are first dipped in a calcium nitrate coagulating solution andthen dipped in the latex fluid for a time sufficient to deposit a filmof about 0.008 inch on the form. The form with the film is then dippedin water to leach out water-soluble impurities. The film is then driedon the forms in a drying oven to remove the water. The forms, with thefilm still intact, is then introduced into a curing oven ofapproximately 100 cubic feet volume and preheated to a temperature ofabout F. to about F. for approximately 30 minutes. Two and one-halfounces (avoirdupois) of sulfur monochloride is introduced on a ceramicsurface in the oven. The gloves are permitted to remain in the resultingsulfur monochloride atmosphere in the oven at a temperature of about 130F. to about 140 F. for a period of about 30 minutes.

At the end of the 30 minute period, the oven is exhausted for 5 minutesand the gloves are removed. The gloves are then stripped from the formswith the inside out.

The gloves are then introduced into a tumbler and tumbled for 15 minutesat a temperature of from about 130 F. to about 140 F. in an atmospherehaving a sulfur monochloride concentration about the same as theconcentration used in the first curing step.

Any excess sulfur monochloride is removed from the gloves by tumblingthem in air for about 10 minutes and then briefly tumbling the gloves inan atmosphere containing ammonia gas.

What is claimed is:

l. A method of making a hyperallergenic article having interior andexterior surfaces and having improved epidermal perception from latexrubber, comprising:

a. coating a form for said article with a coagulant solution for saidlatex,

b. dipping said coated form into a rubber latex fluid free from curingagent therein, to form a coagulant film of said latex upon said form,

c. drying said film to remove water,

d. curing the exterior surface of said film within an atmosphere ofsulfur monochloride vapor at an elevated temperature until the exteriorsurface of said film has been cured enough so that the exterior surfacewill recover its original shape after the film has been stretched andreleased, and stopping said curing before the exterior surface crackswhen said film is stretched,

e. stripping from said form said film with the inside out, and

f. curing said film in an atmosphere of sulfur monochloride vapor at anelevated temperature until both surfaces of said film will recover theiroriginal shape after the film has been stretched and released, andstopping said curing before either surface will crack when the film isstretched.

2. The method of claim 1 wherein the article is a surgeon's glove.

3. The method of claim 1 wherein said curing instep (d.) is carried outfor about 30 minutes.

4. The method of claim 1 wherein said dipping step (b.) is carried outfor a time sufficient to deposit a film of said latex about 0.004-0.0l2inch on said form.

5. The method of claim 1 wherein said coagulant solution comprises asolution of calcium nitrate.

6. The method of claim 1 wherein said latex rubber fluid comprisesnatural latex fluid.

7. An article manufactured in accordance with the process of claim 1.

2. The method of claim 1 wherein the article is a surgeon''s glove. 3.The method of claim 1 wherein said curing in step (d.) is carried outfor about 30 minutes.
 4. The method of claim 1 wherein said dipping step(b.) is carried out for a time sufficient to deposit a film of saidlatex about 0.004-0.012 inch on said form.
 5. The method of claim 1wherein said coagulant solution comprises a solution of calcium nitrate.6. The method of claim 1 wherein said latex rubber fluid comprisesnatural latex fluid.
 7. An article manufactured in accordance with theprocess of claim 1.